There are two Klaytn networks available — Baobab and Cypress, and they server different purposes.
Cypress: Klaytn Mainnet
Cypress is Klaytn’s mainnet in which Governance Council (GC) runs consensus. Cypress is a stable network. Changes can only be introduced to the network if and only if a sufficient number of GC members agree (the number varies depending on the subject). If you plan to launch your product or service, then Cypress is the right place.
Baobab: Klaytn Testnet
On the other hand, Baobab is public testnet for Klaytn. All Klaytn blockchain features will be tested on Baobab before they get deployed to Cypress. If you plan to develop and test your BApp, then Baobab is the right place for you.
When you play with Baobab, you will need some KLAY to pay gas (TX fee). Check out KLAY Faucet for Baobab — you can get 5 KLAY per day for testing purpose. Note that the KLAY you receive from the faucet can only be used in Baobab (remember, Baobab and Cypress are two separate networks).